Type Of La <sub>, Rare Earth Puni <sub> 3 </ Sub> 1-x </ Sub> Of Mg <sub> X </ Sub> Ni <sub> 3-y </ Sub> M <sub> Y < / Sub> Hydrogen Storage Alloy Preparation Process And Microstructure Of The St

In this thesis, the process technology of induction melting and sintering preparation methods on La1-xMgxNi3-yMy alloys and the effects on micro-structural and electrochemical properties and composition of alloys by the process technology has been investigated systematically.From AAS analysis, it shows that the composition of as-cast La3-xMgxNi2.5Co0.5 (x=0.1, 0.33, 0.5, 0.8) alloys synthesized with induction melting preparation methods was controlled well. From XRD, SEM and EDS analyses, it shows that the alloys is composed of the PuNi3, LaNi2 and LaNis phase. The discharge capacity of La0.67Mg0.33Ni2.5Co0.5 alloy, which has the best electrochemical properties, only reached 341mAh/g through 4 charge/discharge cycle numbers. La0.67Mg0.33Ni2.5Co0.5 alloy annealed at 1123 K and 10 hours, the results show that, LaNis phase vanished, LaNi2 phase increase, the discharge capacity has been improved from 341mAh/g to 364mAh/g, the activation decreased from 4 to 5 cycle numbers. The investigation shows that the more suitable process technology of induction melting preparation methods on La3-xMgxNi2.5Co0.5 is as follows: Current is from 300A to 400A.Time is from 150s to 210s. Pressure is 0.4Mpa.The results of the effect of the sintering temperature on the composition, the micro-structural and electrochemical properties of La0.67Mg0.33Ni2.5Co0.5 alloy shows that: when the sintering temperature is under 1023K, the content of Mg element of the alloy is stable, but the sintering reaction is imperfection. When the sintering temperature is over 1123K, the content of Mg element of the alloy decreases obviously, but the sintering reaction is perfection enough.When La0.67Mg0.33Ni2.5Co0.5 alloy was synthesized by sintering with temperature stepwise way, the results shows that: the alloy is composed of the LaNis phase without Mg, the LaNisphase with abundance in Mg and a phase with shortage of Mg on various sintering conditions. When sintering temperature is under 1203K, the amount of Mg of the alloy is stable, while sintering temperature is over 1203K, the amount of Mg of the alloy decreases. The discharge capacity of the alloy varies with structure, when sintering temperature is under 1203K, and the discharge capacity of the alloy manly varies with the amount of Mg of the alloy when sintering temperature is over 1203K. The study shows that the more suitable process technology of sintering preparation methods on La1-xMgxNi3-yMy is asfollows include stable the amount of Mg, average structure, good activation (2cycle numbers) and high discharge capacity (395mAh/g).When La1-xMgxNi2.5Co0.5 (x=0.1,0.2,0.33,0.5,0.67) alloys were synthesized by sintering with temperature stepwise way, the results shows that: The amount of Mg of the alloy is stable. The main phase of the alloys with x<0.5 is LaNi3 phase, but The main phase of the alloys with x>.5 is not LaNi3 phase. The electrochemical properties of the alloys have been improved with x=0.2-0.5.When La0.67Mg0.33Ni2.8M0.2 (M=Co,Fe,Mn,Cr,Cu,Al,Sn) alloys were synthesized by sintering with temperature stepwise way, the results shows that: The main phase of La0.67Mg0.33Ni2.8M0.2 (M=Co,Fe,Mn,Cr,Cu) alloys is LaNi3 phase. The lattice parameter and cell volumes of LaNi3 phaseincrease with the M elements put in. The main phase of La0.67Mg0.33Ni2.8M0.2 (M=Al,Sn) alloys is not LaNi3 phase. The electrochemical properties of La0.67Mg0.33Ni2.8M0.2 alloys including the discharge capacity and activation decrease except La0.67Mg0.33Ni2.8Co0.2 alloy.